Mamiya rb67 65 mm lens got locked on camera.

[mrca]

My RB 67 65 mm lens got locked on my camera and I had to have a camera repair shot pull back the material on the front of the camera to reach the release pin to get it off. I don't remember if he tried mounting it properly with both shutter and mirror cocked and it would come off. I have a call in to him but my question is would a failure to cock both mirror and lens before mounting the lens make it not possible to remove the lens? If I put an uncocked lens on a cocked body, would that jam the lens on the body? Or neither cocked? What could be wrong with a lens to cause it to be unable to be removed and how could I test it without mounting it on camera and getting it stuck again?